# 单分支if语句
# 函数的功能：将字符串str当成有效的表达式来求值并返回计算结果
score = eval(input("请输入成绩分数："))
if score >= 60:
    print("成绩合格:")
# 分别输入数字进行测试
score = eval(input('请输入成绩分数'))
if score < 60:
    print("成绩不合格")
if 60 <= score < 80:
    print("成绩一般")
if 80 <= score <= 90:
    print("成绩良好")
if 90 < score <= 100:
    print("成绩优秀")
# if语句的嵌套使用
score = eval(input('请输入成绩分数'))
if score >= 60:
    print("成绩已及格:")
    if 90 < score <= 100:
        print("成绩优秀")
# 单分支if语句
# 函数的功能：将字符串str当成有效的表达式来求值并返回计算结果
score = eval(input("请输入成绩分数："))
if score >= 60:
    print("成绩合格:")
# 分别输入数字进行测试
score = eval(input('请输入成绩分数'))
if score < 60:
    print("成绩不合格")
if 60 <= score < 80:
    print("成绩一般")
if 80 <= score <= 90:
    print("成绩良好")
if 90 < score <= 100:
    print("成绩优秀")
# if语句的嵌套使用
score = eval(input('请输入成绩分数'))
if score >= 60:
    print("成绩已及格:")
    if 90 < score <= 100:
        print("成绩优秀")
a = 30
if a > 20:
    print("变量a大于20")
else:
    print("变量a不大于20")
# 在if语句中嵌套if-else语句
score = eval(input("请输入成绩分数："))
if score >= 60:
    print("成绩合格")
    if score >= 90:
        print("成绩很好")
    else:
        print("成绩一般")
# 在if-else语句中嵌套if-else语句
score = eval(input("请输入成绩分数："))
if score >= 60:
    print("成绩及格")
    if score >= 90:
        print("成绩很好")
    else:
        print("成绩一般")
else:
    print("成绩不及格")
    if score < 30:
        print("成绩极差")
    else:
        print("成绩较差")
# if-elif-else语句
score = eval(input("请输入一个成绩分数："))
if score >= 90:
    print("成绩优秀")
elif score >= 80:
    print("成绩良好")
elif score >= 70:
    print("成绩中等")
elif score >= 60:
    print("成绩较好")
else:
    print("成绩不合格")
# 练习
a = eval(input("请输入一个年份："))
if a % 4 == 0 and a % 4 == 0 or a % 400 == 0:
    print("是闰年")
else:
    print("不是闰年")
# 条件语句while
i = 1
while i <= 5:
    print("今天星期:", i)
    i = i+1
a = 1
while a <= 100:
    print("今天是第：", a)
    a = a+1
# 计算
n = 1
s = 0
while n <= 100:
    s = s+n
    n = n+1
    print(s)
# 遍历循环
for i in [1, 2, 3, 4, 5]:
    print(i)
# range内置函数
for i in range(10):
    print(i)
    print()
# 条件语句while
i = 1
while i <= 5:
    print("今天星期:", i)
    i = i+1
a = 1
while a <= 100:
    print("今天是第：", a)
    a = a+1
# 计算
n = 1
s = 0
while n <= 100:
    s = s+n
    n = n+1
    print(s)
# 遍历循环for
for i in [1, 2, 3, 4, 5]:
    print(i)
# range内置函数
for i in range(10):
    print(i)
    print()
# while中嵌入while进行表示
i = 1
while i <= 5:
    print("上班时间为：", i)
    i = i+1
    t = 9
    while t <= 17:
        print("时间段：", t, end="   ")
        t = t+1
    print()
# for中嵌入for进行表示
for i in range(1, 6):
    print("上班星期为：", i)
    t = 9
    for t in range(9, 18):
        print("时间段：", t, end="   ")
    print()
# 九九乘法表while嵌套
i = 1
while i <= 9:
    j = 1
    while j <= i:
        print("%d*%d=%d" % (j, i, j*i), end="  ")
        j = j+1
    print()
    i = i+1
# 九九乘法表for嵌套
for i in range(1, 10):
    for j in range(1, i+1):
        print("%d*%d=%d" % (j, i, j*i), end="  ")
    print()
# while 中使用break跳出循环
i = 0
while i <= 5:
    i += 1
    print("星期为：", i)
    if i == 3:
        break

i = 1
while i <= 5:
    if i == 3:
        break
    print("星期为：", i)
    i += 1
# for循环中使用break语句
for i in range(1, 6):
    print("星期为：", i)
    if i == 3:
        break

for i in range(1, 6):
    if i == 3:
        break
    print("星期为：", i)
# while循环中使用continue语句
i = 0
while i < 5:
    i = i + 1
    if i == 4:
        continue
    print("星期为：", i)
# for循环中使用continue语句
for i in range(1, 6):
    if i == 4:
        continue
    print("星期为：", i)